The relationship between hyperoxaluria and urinary calculus disease will be studied in intestinal bypass patients and in animals with segmental bowel resections. A registry of 500 previously bypassed patients and subsequent bypass patients will be established and used to identify a group of oxalate stone formers. Pre and post-operative studies performed on future patients will help distinguish those conditions related to stone formation. Reliable methods for the determination of serum oxalate and for metabolic precursors will be developed and used to quantitate the changes seen after intestinal bypass. Methods of investigating the urinary peculiarities of stone formers, crystal growth and particle aggregation, will be quantitated and applied to the pre and postoperative patients in an attempt to develop a means of preoperative identification of stone formers. Segmental intestinal resections will be performed on dogs and the pathway of hyperoxaluria established utilizing labeled compounds of oxalate and oxalate precursors. The animal studies will also be used to verify the serum levels determined by direct measurement and to establish the method of renal handling of oxalate. Therapeutic measures directed toward the reduction of oxalate excretion and to the prevention of urinary stone formation, both those previously reported and those suggested from this present study, will be applied to the human registry patients.